1. Technical Field
The present disclosure relates to a display device capable of detecting an external proximity object, a drive method thereof, and an electronic apparatus including the display device. More particularly, the present disclosure relates to a display device with a touch detection function capable of detecting an external proximity object based on a change in a capacitance, a drive method thereof, and an electronic apparatus including the display device.
2. Description of the Related Art
Recently, a touch detection device, which is referred to as, so-called a touch panel, capable of detecting an external proximity object is attracting attention. The touch panel is used for a display device with a touch detection function in which the touch panel is mounted on or integrated into the display device such as a liquid-crystal display device. The display device with a touch detection function displays various button images and the like on the display device, and this allows information input using the touch panel instead of normal mechanical buttons. The display device with a touch detection function having such a touch panel does not require an input device such as a keyboard, a mouse, or a keypad, and, therefore, the use thereof in portable information devices such as mobile phones is on the rise as well as in computers.
A method for the touch detection device includes those such as an optical type, a resistive type, and a capacitive type. A capacitive-type touch detection device used for a mobile device or so has a comparatively simple structure and is capable of implementing low power consumption. For example, Japanese Patent Application Laid-open Publication No. 2009-244958 describes a display device in which a common electrode for display originally provided in the display device doubles as one of a pair of touch sensor electrodes and the other electrode (touch detection electrode) is arranged so as to intersect with the common electrode. A capacitance is formed between the common electrode and the touch detection electrode, and the formed capacitance changes according to an external proximity object. The display device is configured to use this feature and analyze a touch detection signal appearing at the touch detection electrode when a drive signal for touch detection is applied to the common electrode, and to thereby detect the external proximity object. The display device performs a display operation by sequentially applying a drive signal to the common electrode and performing line-sequential scanning, and analyzes a touch detection signal appearing at the touch detection electrode in a period of display scanning according to the drive signal, thus performing the touch detection operation.
Japanese Patent Application Laid-open Publication No. 2012-048295 (JP-A-2012-048295) describes a display device with a touch detection function that performs touch detection by sampling a detection result sent from a touch detection element in a period shorter than a period of display scanning in a touch detection operation period different from a display operation period.
It is required that the display device with a touch detection function is not easily affected by noise in terms of operation stability and touch detection sensitivity. For example, when a capacitive-type touch detection device is coupled to an alternating current (AC) power supply, noise (hereinafter, “external noise”) due to the AC power supply or the like is likely to be propagated to the touch detection device entirely caused by a difference between a ground potential of human body and a signal ground potential of the AC power supply. Moreover, if the touch detection function is integrated into the display device or the touch detection device is mounted on the display device, various drive signals used in the display device are likely to be transmitted to the touch detection device as noise (hereinafter, “internal noise”).
In the technology described in JP-A-2012-048295, by sampling the detection result sent from the touch detection element in a period shorter than a period of display scanning in the touch detection operation period different from the display operation period, the touch detection is performed, which enables the influence of the internal noise on the display device to be suppressed. Furthermore, there is a method of providing a filter against the external noise in order to suppress the influence of the external noise on the touch detection device.
However, the filter against the external noise needs to transmit a frequency at which the detection result sent from the touch detection element is sampled, and therefore if the frequency of the external noise and the frequency at which the detection result sent from the touch detection element is sampled are close to each other, an effect to suppress the external noise may be reduced.
For the foregoing reasons, there is a need for a display device with a touch detection function, a drive method of the display device with a touch detection function, and an electronic apparatus that enable performing touch detection with the influence of external noise reduced.